U.S. patent application number 12/068973 was filed with the patent office on 2008-10-30 for desulfurizing device for fuel cell and fuel cell system including the same.
Invention is credited to Jin-Goo Ahn, Man-Seok Han, Ju-Yong Kim, Jun-Sik Kim, Sung-Chul Lee, Yong-Kul Lee.
Application Number | 20080268312 12/068973 |
Document ID | / |
Family ID | 39301297 |
Filed Date | 2008-10-30 |
United States Patent
Application |
20080268312 |
Kind Code |
A1 |
Lee; Yong-Kul ; et
al. |
October 30, 2008 |
Desulfurizing device for fuel cell and fuel cell system including
the same
Abstract
A desulfurizing device for a fuel cell includes a dehydrating
element for absorbing moisture in a hydrocarbon fuel, and a
desulfurizing element for absorbing a sulfur compound included in
the hydrocarbon fuel that flows out of the dehydrating element. In
another embodiment, the desulfurizing device for a fuel cell
includes a dehydrating element for absorbing moisture included in a
fuel, and a desulfurizing element. The desulfurizing element
absorbs a sulfur compound included in the fuel flowing out of the
dehydrating element if temperature of the desulfurizing element is
below a predetermined temperature, and the desulfurizing element
desorbs a sulfur compound included in the desulfurizing element
whenever the desulfurizing element is heated above the
predetermined temperature.
Inventors: |
Lee; Yong-Kul; (Suwon-si,
KR) ; Kim; Ju-Yong; (Suwon-si, KR) ; Han;
Man-Seok; (Suwon-si, KR) ; Kim; Jun-Sik;
(Suwon-si, KR) ; Lee; Sung-Chul; (Suwon-si,
KR) ; Ahn; Jin-Goo; (Suwon-si, KR) |
Correspondence
Address: |
ROBERT E. BUSHNELL
1522 K STREET NW, SUITE 300
WASHINGTON
DC
20005-1202
US
|
Family ID: |
39301297 |
Appl. No.: |
12/068973 |
Filed: |
February 13, 2008 |
Current U.S.
Class: |
429/410 ;
422/262 |
Current CPC
Class: |
B01D 2259/41 20130101;
C10G 2300/202 20130101; C10G 2300/1044 20130101; B01D 53/0407
20130101; B01D 2259/4009 20130101; B01D 2257/30 20130101; B01D
2259/40086 20130101; C10G 2300/1025 20130101; B01D 2253/108
20130101; H01M 8/0675 20130101; B01D 2257/80 20130101; Y02E 60/50
20130101; C10G 25/05 20130101; B01D 2258/05 20130101; H01M
2008/1095 20130101 |
Class at
Publication: |
429/26 ; 422/262;
429/12 |
International
Class: |
H01M 8/00 20060101
H01M008/00; B01D 11/00 20060101 B01D011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 30, 2007 |
KR |
10-2007-0042023 |
Claims
1. A desulfurizing device for a fuel cell comprising: a dehydrating
element through which a fuel flows, the dehydrating element
absorbing moisture included in the fuel; and a desulfurizing
element for absorbing a sulfur compound included in the fuel that
flows out of the dehydrating element.
2. The desulfurizing device of claim 1, wherein the dehydrating
element and the desulfurizing element have a volume ratio ranging
from 1:10 to 5:3.
3. The desulfurizing device of claim 1, wherein the dehydrating
element includes a material selected from the group consisting of
drierite, A-type zeolite, a silica gel, a molecular sieve 3A, a
molecular sieve 4A, a molecular sieve 5A, and combinations
thereof.
4. The desulfurizing device of claim 1, wherein the dehydrating
material has a pore size of less than 0.5 nm.
5. The desulfurizing device of claim 1, wherein the desulfurizing
element comprises a material selected from the group consisting of
Ag supported in hydrophobic zeolite, Cu supported in hydrophobic
zeolite, Zn supported in hydrophobic zeolite, Fe supported in
hydrophobic zeolite, Co supported in hydrophobic zeolite, Ni
supported in hydrophobic zeolite, Ag supported in Y-type zeolite,
Ag supported in .beta.-type zeolite, Ag supported in X-type
zeolite, Cu supported in Y-type zeolite, Cu supported in
.beta.-type zeolite, Cu supported in X-type zeolite, a molecular
sieve 13X, a copper-zinc-based desulfurizing material, and
combinations thereof.
6. The desulfurizing device of claim 1, wherein the desulfurizing
material is ion-exchanged with a metal selected from the group
consisting of a noble metal, a transition element, and combinations
thereof.
7. The desulfurizing device of claim 6, wherein the noble metal
includes a metal selected from the group consisting of Ag, Pt, Pd,
and combinations thereof.
8. The desulfurizing device of claim 6, wherein the transition
element includes a material selected from the group consisting of
Co, Ni, Fe, and combinations thereof.
9. The desulfurizing device of claim 1, wherein the desulfurizing
material has a pore size of more than 0.5 nm.
10. The desulfurizing device of claim 1, wherein the fuel is a
hydrocarbon fuel.
11. The desulfurizing device of claim 10, wherein the hydrocarbon
fuel includes a material selected from the group consisting of
natural gas, city gas, liquid petroleum gas (LPG), naphtha, and
combinations thereof.
12. The desulfurizing device of claim 1, wherein the sulfur
compound includes a material selected from the group consisting of
mercaptan, thiophene, and combinations thereof.
13. A desulfurizing device for a fuel cell comprising: a
dehydrating element through which a fuel flows, the dehydrating
element absorbing moisture included in the fuel; and a
desulfurizing element for absorbing a sulfur compound included in
the fuel flowing out of the dehydrating element if temperature of
the desulfurizing element is below a predetermined temperature, or
for desorbing a sulfur compound included in the desulfurizing
element whenever the desulfurizing element is heated above the
predetermined temperature.
14. The desulfurizing device of claim 13, wherein the predetermined
temperature is higher than 200.degree. C. and lower than
400.degree. C.
15. A fuel cell system comprising: at least one electricity
generating element producing electricity through an electrochemical
reaction of a fuel and an oxidant; a fuel supplier supplying the
electricity generating element with the fuel; an oxidant supplier
supplying the electricity generating element with the oxidant; and
a desulfurizing device coupled to the fuel supplier, the
desulfurizing device comprising: a dehydrating element through
which the fuel flows, the dehydrating element absorbing moisture
included in the fuel; and a desulfurizing element for absorbing a
sulfur compound included in the fuel flowing out of the dehydrating
element.
16. The fuel cell system of claim 15, wherein the fuel is supplied
from the fuel supplier to the electricity generating element
through the desulfurizing device.
17. The fuel cell system of claim 15, further comprising a reformer
for generating hydrogen gas from the fuel, the hydrogen gas being
supplied to the electricity generating element, the fuel being
supplied from a fuel supplier to the reformer through the
desulfurizing device.
18. A fuel cell system comprising: at least one electricity
generating element producing electricity through an electrochemical
reaction of a fuel and an oxidant; a fuel supplier supplying the
electricity generating element with the fuel; an oxidant supplier
supplying the electricity generating element with the oxidant; and
a desulfurizing device coupled to the fuel supplier, the
desulfurizing device comprising: a dehydrating element through
which the fuel flows, the dehydrating element absorbing moisture
included in the fuel; and a desulfurizing element for absorbing a
sulfur compound included in the fuel flowing out of the dehydrating
element if temperature of the desulfurizing element is below a
predetermined temperature, or for desorbing a sulfur compound
included the in the desulfurizing element whenever the
desulfurizing element is heated above the predetermined
temperature.
19. The fuel cell system of claim 18, the fuel cell system further
comprising a plurality of another desulfurizing devices, the
desulfurizing device and the plurality of another desulfurizing
devices being connected in parallel with each other.
20. The fuel cell system of claim 19, wherein at least one among
the desulfurizing device and the plurality of another desulfurizing
devices is not heated to absorb the sulfur compound, while the
remaining ones are heated to desorb a sulfur compound.
21. The fuel cell system of claim 18, wherein the fuel is supplied
from the fuel supplier to the electricity generating element
through the desulfurizing device.
22. The fuel cell system of claim 18, the fuel cell system further
comprising a reformer for generating hydrogen gas from the fuel,
the hydrogen gas being supplied to the electricity generating
element, the fuel being supplied from the fuel supplier to the
reformer through the desulfurizing device.
23. The fuel cell system of claim 22, wherein the desulfurizing
device is heated by gas released from the reformer.
24. The fuel cell system of claim 18, wherein the predetermined
temperature is higher than 200.degree. C. and lower than
400.degree. C.
Description
CLAIM OF PRIORITY
[0001] This application makes reference to, incorporates the same
herein, and claims all benefits accruing under 35 U.S.C. .sctn.119
from an application earlier filed in the Korean Intellectual
Property Office on the Apr. 30, 2007 and there duly assigned Ser.
No. 10-2007-0042023.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a desulfurizing device for
a fuel cell and a fuel cell system including the same. More
particularly, the present invention relates to a desulfurizing
device that can improve desulfurizing efficiency and thereby
decrease the volume of a desulfurizing material and its cost, and a
fuel cell system including the same.
[0004] 2. Description of the Related Art
[0005] A fuel cell is a power generation system for producing
electrical energy using a hydrocarbon-based fuel. Representative
exemplary fuel cells include a polymer electrolyte membrane fuel
cell (PEMFC) and a direct oxidation fuel cell (DOFC).
[0006] The PEMFC has power characteristics that are superior to
those of conventional fuel cells, as well as a lower operating
temperature and faster start and response characteristics. Because
of these advantages, the PEMFC can be applied to a wide range of
applications such as portable electrical power sources for
automobiles, distributed power sources for houses and public
buildings, and small electrical power sources for electronic
devices.
[0007] The polymer electrolyte membrane fuel cell system is
composed of a stack for a fuel cell body (hereinafter referred to
as a "stack" for convenience), a reformer that reforms the fuel to
generate hydrogen gas and supplies the hydrogen gas to the stack,
and an oxidant supplier for supplying an oxidant gas to the stack.
The stack generates electrical energy through an electrochemical
reaction of the reformed gas supplied from the reformer and the
oxidant gas supplied from the oxidant supplier.
[0008] The fuel, such as natural gas, gasoline, diesel, naphtha,
fuel oil, and similar hydrocarbon fuels, may include a small amount
of a sulfur compound odorizer, such as t-butylmercaptan,
terahydrothiophene, isopropylmercaptan, and the like, in order to
prevent a danger that may happen if the fuel leaks. However, the
sulfur compound odorizer can cause severe poisoning to a catalyst
for a modifying reaction when the hydrocarbon fuel is used for a
fuel cell. Accordingly, it should be removed before the modifying
reaction.
SUMMARY OF THE INVENTION
[0009] An embodiment of the present invention provides a
desulfurizing device for a fuel cell having improved desulfurizing
efficiency and thereby decreasing the volume of a desulfurizing
material and also its cost.
[0010] Another embodiment of the present invention provides a fuel
cell system including the desulfurizing device.
[0011] According to one embodiment of the present invention, a
desulfurizing device for a fuel cell includes a dehydrating element
and a desulfurizing element. A fuel flows through the dehydrating
element, and the dehydrating element absorbs moisture included in
the fuel. The desulfurizing element absorbs a sulfur compound
included in the fuel that flows out of the dehydrating element.
[0012] The dehydrating element and the desulfurizing element may be
formed in a volume ratio ranging from 1:10 to 5:3, but according to
another embodiment of the present invention, they may have a volume
ratio of 1:5 to 5:5.
[0013] The dehydrating element may include a desulfurizing material
selected from the group consisting of drierite, A-type zeolite, a
silica gel, a molecular sieve 3A, a molecular sieve 4A, a molecular
sieve 5A, and combinations thereof.
[0014] The desulfurizing material may have a pore size of less than
0.5 nm, but according to another embodiment, it may have a pore
size ranging from 0.1 nm to 0.4 nm.
[0015] The desulfurizing element may include a desulfurizing
material selected from the group consisting of Ag, Cu, Zn, Fe, Co,
or Ni supported in hydrophobic zeolite; Ag or Cu supported in
Y-type zeolite, .beta.-type zeolite, or X-type zeolite; a molecular
sieve 13X; a copper-zinc-based desulfurizing material; copper
supported on a porous carrier; and combinations thereof.
[0016] The desulfurizing material may be ion-exchanged with a metal
selected from-the group consisting of a noble metal, a transition
element, and combinations thereof. The noble metal may be selected
from the group consisting of Ag, Pt, Pd, and combinations thereof,
and the transition element may be selected from the group
consisting of Co, Ni, Fe, and combinations thereof.
[0017] The desulfurizing material may have a pore size of more than
0.5 nm, but according to another embodiment, it may have one
ranging from 0.5 nm to 1.0 nm.
[0018] The fuel may include a hydrocarbon fuel. The hydrocarbon
fuel may be selected from the group consisting of natural gas, city
gas, liquid petroleum gas (LPG), naphtha, and combinations thereof.
The sulfur compound may be selected from the group consisting of
mercaptan, thiophene, and a combination thereof.
[0019] According to another embodiment of the present invention, a
desulfurizing device for a fuel cell includes a dehydrating element
and a desulfurizing element. A fuel flows through the dehydrating
element, and the dehydrating element absorbs moisture included in
the fuel. The desulfurizing element absorbs a sulfur compound
included in the fuel flowing out of the dehydrating element if
temperature of the desulfurizing element is below a predetermined
temperature, or desorbs a sulfur compound included in the
desulfurizing element whenever the desulfurizing element is heated
above the predetermined temperature.
[0020] The predetermined temperature may be higher than 200.degree.
C. and lower than 400.degree. C.
[0021] According to another embodiment of the present invention, a
fuel cell system is provided. The fuel cell system includes at
least one electricity generating element producing electricity
through an electrochemical reaction of a fuel and an oxidant, a
fuel supplier supplying the electricity generating element with the
fuel, an oxidant supplier supplying the electricity generating
element with the oxidant, and a desulfurizing device coupled to the
fuel supplier. The desulfurizing device includes a dehydrating
element and a desulfurizing element. The fuel flows through the
dehydrating element, and the dehydrating element absorbs moisture
included in the fuel. The desulfurizing element absorbs a sulfur
compound included in the fuel that flows out of the dehydrating
element.
[0022] The fuel can be supplied from the fuel supplier to the
electricity generating element through the desulfurizing
device.
[0023] The fuel cell system may further include a reformer that can
generate hydrogen gas from the fuel. Herein, the fuel may be
supplied from the fuel supplier to the reformer through the
desulfurizing device.
[0024] According to another embodiment, a fuel cell system includes
at least one electricity generating element producing electricity
through an electrochemical reaction of a fuel and an oxidant, a
fuel supplier supplying the electricity generating element with the
fuel, an oxidant supplier supplying the electricity generating
element with the oxidant, and a desulfurizing, device coupled to
the fuel supplier. The desulfurizing device includes a dehydrating
element and a desulfurizing element. The fuel flows through the
dehydrating element, and the dehydrating element absorbs moisture
included in the fuel. The desulfurizing element absorbs a sulfur
compound included in the fuel flowing out of the dehydrating
element if temperature of the desulfurizing element is below a
predetermined temperature, or desorbs a sulfur compound included in
the desulfurizing element whenever the desulfurizing element is
heated above the predetermined temperature.
[0025] The fuel cell system may include a plurality of another
desulfurizing devices. The desulfurizing device and the plurality
of another desulfurizing devices are connected in parallel with
each other. At least one among the desulfurizing device and the
plurality of another desulfurizing devices is not heated to absorb
the sulfur compound, while the remaining ones are heated to desorb
a sulfur compound.
[0026] The fuel can be supplied from the fuel supplier to the
electricity generating element through the desulfurizing
device.
[0027] The fuel cell system may further include a reformer that can
generate hydrogen gas from the fuel. Herein, the fuel may be
supplied from the fuel supplier to the reformer through the
desulfurizing device. The desulfurizing device may be heated by gas
released from the reformer. The predetermined temperature may be
higher than 200.degree. C. and lower than 400' C.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] A more complete appreciation of the invention and many of
the attendant advantages thereof, will be readily apparent as the
same becomes better understood by reference to the following
detailed description when considered in conjunction with the
accompanying drawings in which like reference symbols indicate the
same or similar components, wherein:
[0029] FIG. 1 is a schematic view showing a structure of a fuel
cell system constructed as one embodiment of the present
invention;
[0030] FIG. 2 is an exploded perspective view showing the structure
of the stack illustrated in FIG. 1;
[0031] FIG. 3 is a cross-sectional view showing the structure of
the desulfurizing device illustrated in FIG. 1;
[0032] FIG. 4 is a cross-sectional view of the desulfurizing device
constructed as a second embodiment of the present invention;
[0033] FIG. 5 is a cross-sectional view of the desulfurizing device
of the second embodiment of the present invention that is operated
while the device is being heated;
[0034] FIG. 6 shows a gas chromatography analysis result of a
commercially available liquid petroleum gas; and
[0035] FIG. 7 shows a performance analysis result of a
desulfurizing device according to Comparative Examples 1 and 2 and
Example 1.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0036] An embodiment of the present invention will hereinafter be
described in detail with reference to the accompanying
drawings.
[0037] The desulfurizing device for a fuel cell according to a
first embodiment includes a dehydrating element selectively
absorbing moisture included in a fuel cell, and a desulfurizing
element absorbing a sulfur compound included in the fuel that
passed through the dehydrating element.
[0038] When the fuel includes an unpurified fuel, such as natural
gas, city gas, liquid petroleum gas (LPG), naphtha, and the like,
the unpurified fuel includes a small amount of an organic sulfur
compound that is naturally generated, or a sulfur compound, such as
mercaptan or thiophene, that is added as an odorizer. This small
amount of the sulfur compound can generate hydrogen, which can
damage all catalysts by poisoning them. Accordingly, the amount of
sulfur compound included in the fuel should be decreased to less
than 100 ppm to suppress the above damage.
[0039] A conventional desulfurizing device for a fuel cell includes
a single filter layer including a desulfurizing material, so that
the desulfurizing material can remove the sulfur compound included
in the fuel. However, the fuel also includes moisture, and the
moisture is competitively absorbed by the desulfurizing material,
sharply decreasing the absorption performance of the sulfur
compound.
[0040] According to an embodiment of the present invention, a
desulfurizing device includes a dehydrating element for selectively
absorbing moisture, through which a fuel can pass to remove the
moisture before it is supplied to a desulfurizing element,
resultantly improving its desulfurization performance.
[0041] The dehydrating element and the desulfurizing element may
have a different volume ratio depending on the amount ratio of
moisture and the sulfur compound included in the fuel and
performance of the dehydrating element. In other words, if a fuel
includes moisture and a sulfur compound in the same ratio, the
dehydrating and desulfurizing elements can have the same volume
ratio. However, if the dehydrating element has excellent
performance, it can have a smaller volume than the desulfurizing
element.
[0042] Considering a commercially available fuel component and
better performance of a dehydrating material than a desulfurizing
material, the dehydrating and desulfurizing elements may have a
volume ratio ranging from 1:10 to 5:3, but according to another
embodiment, they may have a volume ratio ranging from 1:5 to 5:5.
In other words, in the desulfurizing device, the volume ratio of
the dehydrating element to the desulfurizing element can be a ratio
such as 1:10, 1:5, 2:5, 3:5, 4:5, 5:5, 5:4, or 5:3.
[0043] In general, when a fuel includes less moisture, it can have
better efficiency. However, an actual fuel includes moisture and a
sulfur compound in a similar volume ratio. Accordingly, the above
ratios between the dehydrating and desulfurizing elements can be
decided considering a similar ratio between moisture and the sulfur
compound and, at most, considering 10 times better performance of
the dehydrating element than the desulfurizing element.
[0044] The dehydrating element includes a dehydrating material
selectively absorbing moisture. The dehydrating material may
include any conventional one. The dehydrating material may be
particularly selected from the group consisting of drierite; A-type
zeolite; a silica gel; 3A, 4A, and SA molecular sieves; and a
combination thereof. The dehydrating material is conventionally
well-known and does not need more detailed description.
[0045] The dehydrating material can have various pore sizes to
selectively remove moisture, considering the molecular size of the
sulfur compound. However, considering the molecular size of a
conventional odorizer, the dehydrating material may have a pore
size of less than 0.5 nm. According to another embodiment, it may
have a pore size ranging from 0.1 to 0.4 nm. In other words, the
dehydrating material may have a pore size of 0.1 nm, 0.2 nm, 0.3
nm, 0.4 nm, or 0.5 nm. When the dehydrating material has a pore
size within the above range, it has little physical and chemical
absorption force against the sulfur compound, and thereby can more
selectively absorb moisture.
[0046] The desulfurizing element includes a desulfurizing material
absorbing a sulfur compound. The desulfurizing material may include
any conventional one. In particular, the desulfurizing material may
include one selected from the group consisting of Ag, Cu, Zn, Fe,
Co, or Ni supported in hydrophobic zeolite; Ag or Cu supported in
Y-type zeolite, .beta.-type zeolite, or X-type zeolite; a molecular
sieve 13X; a copper-zinc-based desulfurizing material; copper
supported on a porous carrier; or the like. The desulfurizing
materials are conventionally well-known and do not need more
detailed description.
[0047] The desulfurizing material may be ion-exchanged with a metal
selected from the group consisting of a noble metal, a transition
element, and combinations thereof. When the desulfurizing material
is ion-exchanged by a metal selected from the group consisting of a
noble metal, a transition element, and combinations thereof, a
sulfur compound is absorbed in the desulfurizing material, and
thereby changes the color of the desulfurizing material.
[0048] In general, a desulfurizing material is necessarily replaced
at particular intervals. However, it is hard to decide the
replacement time for a common desulfurizing material. At present,
the replacement time for a desulfurizing material is decided by
calculating the predictable absorption amount against its
performance. However, different fuels include different amounts of
a sulfur compound, and therefore, there is a problem of
continuously checking the cumulative time of the desulfurizing
material.
[0049] On the other hand, a desulfurizing material, which is
ion-exchanged with a metal selected from the group consisting of a
noble metal, a transition element, and combinations thereof, has
the advantage of demonstrating its replacement time through a color
change. The noble metal may be selected from the group consisting
of Ag, Pt, Pd, and combinations thereof. The transition element may
be selected from the group consisting of Co, Ni, Fe, and
combinations thereof.
[0050] The desulfurizing material ion-exchanged with a metal can be
included as the whole amount of the desulfurizing element, or a
small amount of the desulfurizing material ion-exchanged with a
metal can be blended with a desulfurizing material that is not
ion-exchanged with the metal. Because the desulfurizing material
ion-exchanged with a metal is more expensive than the desulfurizing
material not ion-exchanged with the metal, it could be economically
advantageous to use a small amount of the desulfurizing material
ion-exchanged with a metal.
[0051] The desulfurizing material can have various pore sizes to
efficiently remove the sulfur compound, considering the molecular
size of the sulfur compound. However, considering the molecular
size of a popular odorizer, the desulfurizing material may have a
pore size of more than 0.5 nm. According to another embodiment, it
may have a pore size ranging from 0.5 to 1.0 nm. In other words,
the desulfurizing material can have various pore sizes such as 0.5
nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, and 1.0 nm. When the
desulfurizing material has a pore size within the above range, it
can better absorb mercaptan and thiophene used as the odorizer. On
the other hand, when it has too large a pore size, it may have poor
physical absorption and a decreased surface area.
[0052] The fuel may be a hydrocarbon fuel. The hydrocarbon fuel may
include any conventional one used for a fuel cell. When the
hydrocarbon fuel is selected from the group consisting of natural
gas, city gas, liquid petroleum gas (LPG), naphtha, and
combinations thereof, it may further include a naturally-generated
organic sulfur compound or an artificially-added odorizer.
[0053] According to a second embodiment of the present invention, a
desulfurizing device includes a dehydrating element selectively
absorbing moisture included in a fuel and a desulfurizing element
absorbing a sulfur compound included in the fuel that passed
through the dehydrating element. The desulfurizing element includes
a desulfurizing material that absorbs a sulfur compound when the
element is not heated, and desorbs a sulfur compound if the element
is heated.
[0054] In general, a desulfurizing material is necessarily replaced
at particular intervals. However, it is hard to decide a
replacement time for a common desulfurizing material. At present,
the replacement time for a desulfurizing material is decided by
calculating predictable absorption amount against the performance.
However, since different fuels include various amounts of the
sulfur compound, there is a problem of continually checking the
cumulative time of the desulfurizing material.
[0055] According to the second embodiment of present invention, a
desulfurizing device is a recycling type device including a
desulfurizing element absorbing a sulfur compound when not heated,
and desorbing the sulfur compound when heated. Since the
desulfurizing device can half-permanently maintain its removal
function of the sulfur compound, it does not need to have the
desulfurizing material replaced and can alleviate performance
deterioration of a system due to saturation of the desulfurizing
material.
[0056] The heating is performed at a temperature of 200 to
400.degree. C. When the heating is performed at a temperature of
lower than 200.degree. C., it may slow down the desorption reaction
or completely hinder it. On the other hand, when it is performed at
a temperature of higher than 400.degree. C., it may change a
property of the desulfurizing material and a container for a
desulfurization filter.
[0057] Examples of the desulfurizing material that absorbs the
sulfur compound when the material is not heated, and desorbs the
sulfur compound if the material is heated may be selected from the
group consisting of Ag, Cu, Zn, Fe, Co, or Ni supported on
hydrophobic zeolite; Ag or Cu supported in Y-type zeolite,
.beta.-type zeolite, or X-type zeolite; a molecular sieve 13X; a
copper-zinc-based desulfurizing material; copper supported on a
porous carrier; or the like.
[0058] The desulfurizing element, absorbing the sulfur compound
when not heated and desorbing the sulfur compound when heated, has
acid sites, and thereby can have an acid-base combination with the
sulfur compound. Accordingly, it can easily absorb the sulfur
compound, and also can smoothly desorb the sulfur compound by
heating the element at a temperature ranging from 200 to
400.degree. C.
[0059] In addition, when it is supported on a metal component, the
metal component has a covalent bond with the sulfur compound,
improving its absorption performance. According to the embodiment
of the present invention, the metal component may be Ag or
transition elements.
[0060] According to a third embodiment of the present invention,
the provided is a fuel cell system that includes at least one
electricity generating element producing electricity through a
reaction of a fuel and an oxidant, a fuel supplier supplying the
electricity generating element with the fuel, an oxidant supplier
supplying the electricity generating element with the oxidant, and
a desulfurizing device including a dehydrating element selectively
absorbing moisture included in the fuel and a desulfurizing element
absorbing a sulfur compound included in the fuel. The fuel may be
supplied from the fuel supplier to the electricity generating
element through the desulfurizing device.
[0061] A fuel cell system according to a fourth embodiment of the
present invention includes at least one electricity generating
element producing electricity through an electrochemical reaction
of a fuel and an oxidant, a fuel supplier supplying the electricity
generating element with the fuel, an oxidant supplier supplying the
electricity generating element with the oxidant, a dehydrating
element selectively absorbing moisture included in the fuel and a
desulfurizing element absorbing a sulfur compound included in the
fuel that passed through the dehydrating element. The desulfurizing
element includes a desulfurizing material that absorbs a sulfur
compound when not heated and desorbs a sulfur compound with
heated.
[0062] The fuel cell system includes a plurality of desulfurizing
devices that are connected in parallel with each other. While at
least one of a plurality of desulfurizing devices is not heated to
absorb a sulfur compound, the remaining ones among the plurality of
desulfurizing devices may be heated to desorb a sulfur compound.
The fuel may be supplied from the fuel supplier to the electricity
generating element via the desulfurizing device.
[0063] The fuel cell system may further include a reformer that can
generate hydrogen gas from the fuel. Herein, the fuel may be
supplied from the fuel supplier to the reformer through the
desulfurizing device. The desulfurizing device can be heated by
using a released gas from a reformer. The desulfurizing device of
the present invention, however, can be constructed to have another
heating source other than the reformer.
[0064] Hereinafter, one embodiment of the present invention is
illustrated in more detail with reference to the accompanying
drawings, so that those who have common knowledge in this related
field can easily understand. However, the present invention can be
realized in various ways and is not limited thereto.
[0065] FIG. 1 is a schematic cross-sectional view showing a
structure of a fuel cell system 100 constructed as one embodiment
of the present invention, FIG. 2 is an exploded perspective view
showing a structure of a stack 10 illustrated in FIG. 1, and FIG. 3
is a cross-sectional view showing a structure of a desulfurizing
device 20 illustrated in FIG. 1. Referring to FIGS. 1 to 3, the
schematic structure of a fuel cell system 100 according to one
embodiment of the present invention is described as follows.
[0066] Referring to FIG. 1, the fuel cell system 100 is fabricated
by employing a polymer electrode membrane fuel cell (PEMFC), which
modifies a fuel including hydrogen, and thereby generates hydrogen
and also electricity through oxidation of the hydrogen and
reduction of an oxidant. In the fuel cell system 100, an oxidant
can be air including oxygen or oxygen kept in a separate
storage.
[0067] According to the embodiment of the present invention, a fuel
cell system 100 includes an electricity generating element 11
generating electricity through reduction of an oxidant and
oxidation of a gas modified through a reformer 30, a fuel supplier
50 supplying the reformer 30 with a fuel, the reformer 30
generating hydrogen by modifying the fuel and supplying the
electricity generating element 11 with the hydrogen, an oxidant
supplier 70 supplying the electricity generating element 11 and the
reformer 30 with the oxidant, and a desulfurizing device 20
absorbing a sulfur compound included in the fuel. A plurality of
the electricity generating elements 11 is stacked together to form
the stack 10.
[0068] When the fuel cell system 100 with the above structure is
operated, hydrogen generated from the reformer 30 is supplied to
the electricity generating elements 11 of the stack 10, and an
oxidant is supplied to the electricity generating elements 11 from
the oxidant supplier 70. Then, electricity is generated through
oxidation of the hydrogen and reduction of the oxidant in the stack
10.
[0069] The reformer 30 has a structure of generating hydrogen from
a fuel including the hydrogen and supplying the hydrogen to the
stack 10. The reformer 30 generates hydrogen through steam
reforming (SR), an autothermal reforming reaction (ATR), or partial
oxidation (POX), and supplies the hydrogen to the stack 10. In
addition, the reformer 30 can further include a carbon monoxide
reducing element (not illustrated) selectively oxidizing carbon
monoxide.
[0070] On the other hand, a fuel supplier 50 supplying the reformer
30 with the fuel includes a fuel tank 51 storing the fuel and a
fuel pump 53 connected to the fuel tank 51 and releasing the fuel
therefrom. The oxidant supplier 70 includes an oxidant pump 71
absorbing the oxidant with a predetermined pumping force and
respectively supplying the oxidant to the electricity generating
element 11 and the reformer 30. As shown in FIG. 1, the oxidant
supplier 70 has a structure of supplying the oxidant to the stack
10 and the reformer 30 through a single oxidant pump 71 but can be
equipped with a pair of oxidant pumps respectively connected to the
stack 10 and the reformer 30.
[0071] Referring to FIG. 2, the stack 10 is formed by stacking
electricity generating elements 11. The electricity generating
element 11 can be used to form a unit fuel cell by positioning a
membrane-electrode assembly (MEA) 12 in the center and disposing a
separator (or a bipolar plate) 16 at each side thereof.
[0072] Herein, the membrane-electrode assembly 12 has a
predetermined active area for an electrochemical reaction of
hydrogen and an oxidant, and includes an anode at one side and a
cathode at the other side and an electrolyte membrane therebetween.
Herein, the anode plays a role of oxidizing hydrogen, and thereby
changing it into protons and electrons. On the other hand, the
cathode reduces the protons and an oxidant, and thereby generates
heat at a predetermined temperature and moisture. In addition, the
electrolyte membrane plays a role of transferring protons produced
at the anode to the cathode. The separator 16 plays a role of
supplying the hydrogen and the oxidant to both sides of the
membrane-electrode assembly 12, and also works as a conductor
connecting the anode and the cathode in series.
[0073] Referring to FIG. 3, the desulfurizing device 20 can be
fabricated as a pipe-shaped reactor 29 with a predetermined fuel
inlet 21 and fuel outlet 22. The desulfurizing device 20 includes a
dehydrating element 23 including a dehydrating material selectively
absorbing moisture included in the fuel and a desulfurizing element
25 including a desulfurizing material 26 selectively absorbing a
sulfur compound included in the fuel. In addition, the
desulfurizing device 20 can further include filters 27 and 28
positioned at the fuel inlet 21 and the fuel outlet 22. The filters
27 and 28 can be a mesh in order to completely catch a dehydrating
material 24 and a desulfurizing material 26.
[0074] The fuel inlet 21 is connected to the fuel supplier 50, and
the fuel outlet 22 can be connected to the reformer 30. In
addition, the dehydrating element 23 may partially take an internal
space of the pipe-shaped reactor 29 from the fuel inlet 21. The
desulfurizing element 25 also may partially take an internal space
of the pipe-shaped reactor 29 from the dehydrating element 23 to
the fuel outlet 22. Accordingly, the fuel is injected through the
fuel inlet 21 to the pipe-shaped reactor 29, passes the dehydrating
element 23 and thereafter the desulfurizing element 25, and is
released through the fuel outlet 22 out of the pipe-shaped reactor
29.
[0075] FIG. 4 is a cross-sectional view of the desulfurizing device
of a second embodiment of the present invention that is operated
while the device is not heated, and FIG. 5 is a cross-sectional
view of the desulfurizing device according to the second embodiment
of the present invention that is operated while the device is
heated. In FIGS. 4 and 5, the same members are assigned as the same
reference numerals as in FIG. 3.
[0076] Referring to FIG. 4, the desulfurizing device 400 includes a
desulfurizing element that absorbs a sulfur compound when the
desulfurizing element is not heated and desorbs a sulfur compound
when the element is heated. The desulfurizing device 400 includes a
first valve 431 and a second valve 432. The first valve 431 is
capable of alternatively connecting the fuel inlet 21 or a carrier
gas inlet 411 to the pipe-typed reactor 29, and a second valve 432
is capable of alternatively connecting the fuel outlet 22 or the
carrier gas outlet 412 to the pipe-typed reactor 29.
[0077] A carrier gas that can be supplied through the carrier gas
inlet 411 delivers a sulfur compound desorbed from a desulfurizing
material and may include air or an oxidant used for a fuel cell
system.
[0078] In addition, when the desulfurizing device 400 is heated by
exchanging heat with a reformer-released gas, it may further
include a heating gas inlet 421 and a heating gas outlet 422 for
flowing the reformer-released gas and a housing 440 surrounding the
pipe-type reactor. When the desulfurizing device 400 is not heated,
the first valve 431 connects the fuel inlet 21 to the pipe-type
reactor 29, so that a fuel can be supplied inside the pipe-shaped
reactor 29, and then, a desulfurizing material can absorb a sulfur
compound included in the fuel. In addition, the second valve 432
connects the pipe-type reactor 29 to the fuel outlet 22, so that
the fuel can be released through the fuel outlet 22.
[0079] Referring to FIG. 5, when the desulfurizing device 400 is
heated, the first valve 431 connects the carrier gas inlet 411 to
the pipe-shaped reactor 29, so that carrier gas can be supplied
inside the reactor 29, and thereby carries a sulfur compound
desorbed from the desulfurizing material. In addition, the second
valve 432 connects the pipe-shaped reactor 29 to the carrier gas
outlet 412, so that carrier gas can be released through the carrier
gas outlet 412.
[0080] Gas released from the reformer, which is over 250.degree.
C., is delivered into the housing 440 through the heating gas inlet
421. The gas heats a desulfurizing element while passing the inside
of the housing 440, and then is released through the heating gas
outlet 422.
[0081] The following examples illustrate the present invention in
more detail. However, the following examples are only exemplary
embodiments of the present invention and it is not necessarily
limited thereto.
[0082] Sulfur compound analysis of commercially-available liquid
petroleum gas
[0083] A sulfur compound included in petroleum gas was examined
regarding its kind and amount by using gas chromatography (GC). The
result is shown in FIG. 6. Referring to FIG. 6, a sulfur compound
such as dimethylsulfide, t-butylmercaptan, and tetrahydrothiophene
was detected. Its amount was about 50 ppm.
[0084] Fabrication of a desulfurizing device and evaluation of its
performance
COMPARATIVE EXAMPLE 1
[0085] A molecular sieve 4A (UOP Co.) was stuffed in a reactor, and
then, a commercially available liquid petroleum gas was allowed to
flow through it. In the reactor, a sulfur compound was examined to
detect the saturated absorption movement by using a sulfur
chemiluminescence detector (SCD).
COMPARATIVE EXAMPLE 2
[0086] A sulfur compound was examined to detect its saturated
absorption movement with the same method as in Comparative Example
1 except that a molecular sieve 13X (UOP Co.) was stuffed in a
reactor.
EXAMPLE 1
[0087] A sulfur compound was examined to detect its saturated
absorption movement with the same method as in Comparative Example
1 except that a molecular sieve 4A and a molecular sieve 13X were
stuffed in a reactor in a volume ratio of 5:5, and then, a
commercially available liquid petroleum gas was allowed to flow
through it.
EXAMPLE 2
[0088] A sulfur compound was examined to detect its saturated
absorption movement with the same method as in Example 1 except
that a molecular sieve 4A and a molecular sieve 13X were stuffed in
a reactor in a volume ratio of 4:5.
EXAMPLE 3
[0089] A sulfur compound was examined to detect its saturated
absorption movement with the same method as in Example 1 except
that a molecular sieve 4A and a molecular sieve 13X were stuffed in
a reactor in a volume ratio of 3:5.
EXAMPLE 4
[0090] A sulfur compound was examined to detect its saturated
absorption movement with the same method as in Example 1 except
that a molecular sieve 4A and a molecular sieve 13X were stuffed in
a reactor in a volume ratio of 2:5.
EXAMPLE 5
[0091] A sulfur compound was examined to detect its saturated
absorption movement with the same method as in Example 1 except
that a molecular sieve 4A and a molecular sieve 13X were stuffed in
a reactor in a volume ratio of 1:5.
EXAMPLE 6
[0092] A sulfur compound was examined to detect its saturated
absorption movement with the same method as in Example 1 except
that a molecular sieve 4A and a molecular sieve 13X were stuffed in
a reactor in a volume ratio of 1:10.
EXAMPLE 7
[0093] A sulfur compound was examined to detect its saturated
absorption movement with the same method as in Example 1 except
that a molecular sieve 4A and a molecular sieve 13X were stuffed in
a reactor in a volume ratio of 5:4.
EXAMPLE 8
[0094] A sulfur compound was examined to detect its saturated
absorption movement with to the same method as in Example 1 except
that a molecular sieve 4A and a molecular sieve 13X were stuffed in
a reactor in a volume ratio of 5:3.
EXAMPLE 9
[0095] A sulfur compound was examined to detect its saturated
absorption movement with the same method as in Example 1 except
that a molecular sieve 4A and a molecular sieve 13X ion-exchanged
with Ag were stuffed in a reactor in a volume ratio of 4:5.
EXAMPLE 10
[0096] A sulfur compound was examined to detect its saturated
absorption movement with the same method as in Example 1 except
that a molecular sieve 4A and a molecular sieve 13X ion-exchanged
with Co were stuffed in a reactor in a volume ratio of 4:5.
EXAMPLE 11
[0097] A sulfur compound was examined to detect its saturated
absorption movement with the same method as in Example 1 except
that a molecular sieve 4A and a molecular sieve 13X ion-exchanged
with Ni were stuffed in a reactor in a volume ratio of 4:5.
EXAMPLE 12
[0098] A sulfur compound was examined to detect its saturated
absorption movement with the same method as in Example 1 except
that a molecular sieve 4A and a molecular sieve 13X ion-exchanged
with Fe were stuffed in a reactor in a volume ratio of 4:5.
[0099] The desulfurizing devices of Comparative Examples 1 and 2
and Example 1 were examined to detect the saturated absorption
movement of a sulfur compound by using a sulfur chemiluminescence
detector (SCD). The results are shown in FIG. 7.
[0100] Referring to FIG. 7, the saturated movement of a sulfur
compound was detected in the desulfurizing device of Comparative
Example 1 after 1.5 hours since the beginning of the test. This
movement seemed to come from the small pore size of the absorption
material. In other words, since the sulfur compound has a bigger
molecular size than the pore size of the absorption material, it
must have been hardly absorbed therein. As for the desulfurizing
device of Comparative Example 2, the saturated movement of the
sulfur compound was detected after 20 hours.
[0101] As for the desulfurizing device of Example 1, the saturated
movement of the sulfur compound was detected after much longer
time. Accordingly, the desulfurizing device of Example 1 turned out
to have over twice as improved absorption performance than the one
of Comparative Example 1. This is more than 5 times based on a
predetermined level. The desulfurizing devices of Examples 2 to 12
had a similar saturated absorption movement of a sulfur compound to
that of the one of Example 1.
[0102] For the desulfarizing devices of Examples 9 to 12, the
desulfurizing materials therein were found to have a color change
as the sulfur compounds were absorbed. In particular, for the
desulfurizing device of Example 11, the desulfurizing material
therein was yellowish at first and then turned into dark brown, as
the sulfur compound was absorbed.
[0103] Therefore, the present invention provides a desulfurizing
device additionally including a dehydrating element that can
selectively absorb moisture, and thereby can contribute to
improving desulfurizing efficiency. In addition, it can decrease
the volume of desulfurizing materials, and thereby a cost.
[0104] While this invention has been described in connection with
what is presently considered to be practical exemplary embodiments,
it is to be understood that the invention is not limited to the
disclosed embodiments, but, on the contrary, is intended to cover
various modifications and equivalent arrangements included within
the spirit and scope of the appended claims.
* * * * *